Photon Round-Trip Times and the Equivalence Principle

Where there is no gravity, I consider a linearly accelerating frame in which the proper acceleration at each spatial point does not vary with time and the proper acceleration is the same throughout the spatial coordinates. Then I consider the round‐trip time for a photon between two given spatial coordinate points. The theory of general relativity predicts that the trip time is a constant with respect to time. Contrary to this prediction, I analyze the motion of the photon in an inertial frame and show a discrepancy of order a τ/c, where a is the proper acceleration; τ is the photon round‐trip time in the accelerating frame, which also indicates the spatial size of the accelerating frame; and c is the speed of light.